It has heretofore been described in the prior art to provide rotary engines of the type including two or more tangentially contacting rotors, a power rotor and a sealing rotor, which rotate about parallel axes with their peripheral surfaces in tangential contact. The power rotor is formed with a protuberance or piston extending outwardly into a chamber defined by a surrounding housing bore within which is mounted the power rotor. A corresponding pocket or recess is formed on the sealing rotor so that as the piston rotates about and into engagement with the sealing rotor, the piston is received within the recess. A working fluid under pressure is introduced through intake porting into the space behind the piston and ahead of the point of contact of the rotors such as to cause rotation of the power rotor by expansion of the working fluid, producing a force acting on the power rotor tending to produce rotation. At the end of the expansion stroke, the piston moves past an exhaust port, allowing exhausting of the fluid prior to initiation of another cycle.
This design has many advantages, i.e., simplicity; the relatively small number of working parts of simple and rugged construction; freedom from vibration since the working parts undergo only rotation; and a relatively efficient thermodynamic cycle in which relatively complete expansion of the working fluid is enabled. In the case of steam as a working fluid, the relatively complete expansion thereof largely obviates the necessity for a large condenser, since the steam is largely condensed upon being exhausted from the working chamber.
However, despite these advantages, several problems are associated with this design. Among these are the rapid valving action occurring tends to produce large accelerating and decelerating forces due to the rapid valving action necessary in controlling the admission of the working fluid. Again, the valving action may involve the use of valving ports formed on a cover plate or other similar structure disposed adjacent one face of the power rotor with a corresponding valving recess moving into registry with the valve port at the appropriate point in the cycle of the power rotor rotation. This creates a tendency for the working fluid pressure to be exerted on one face creating a pressure force acting on the rotor tending to increase the friction forces, reducing the efficiency, durability and reliability of the engine.
A further difficulty that may be encountered under part throttle conditions is that as the piston rotates to a point intermediate the location where the exhaust port is located, the working fluid may be expanded to the point whereat a subatmospheric or vacuum pressure is created in the working chamber behind the piston. This creates a drag acting on the rotor, working against a pressure differential between atmospheric pressure and the pressure behind the piston. Similarly, a vacuum condition can develop just at the point whereat the piston exits the recess, creating a further drag on the engine, tending to reduce its overall operating efficiency.
Another major difficulty has been associated with the necessity to produce a face seal on the rotor face and adjacent cover plate structure in order to prevent bypassing leakage of the working medium past the mating faces thereof. Such seals must be extremely durable, relatively effective, and not be subject to wear such as to create substantial maintenance burdens associated with operation of the engine. Again, the cost of the seal must be moderate in order to achieve the overall objectives of the design of relatively low cost and simple configuration.
Associated with such fluid pressure devices is a problem defined as a wire drawing effect typically experienced with a throttle valve, that is, the fluid pressure acting on the valving member as the opening and closing of a valve port produces losses in the system in flowing through a small orifice. Also, fluid pressure acting on the valving tends to force it into extremely tight engagement with the port face increasing the wear and effort required in operating the throttle valve. On the other hand, the fluid pressure forces are generally relied on in order to produce a good sealing contact with a valve member in the valve port face.
Accordingly, it is an object of the present invention to provide a displacement turbine engine of the general type described but in which the pressure surges due to the operation of the valving means must be relied on to control the admission of the working fluid pressure to the working chamber.
It is a further object of the present invention to provide such displacement turbine engine in which the pressure unbalance forces acting on the power rotor are largely avoided even though valving consisting of ports located on one face of the power rotor are employed to control the admission of working fluid to the working chamber.
Yet another object of the present invention is to provide such displacement turbine in which the inefficiencies created by vacuum conditions developing during part throttle or other engine operating conditions are obviated.
It is a still further object of the present invention to provide a simple and highly effective sealing configuration arrangement for such engines or similar applications in which a condensing fluid such as steam is employed as a working medium.
It is yet another object of the present invention to provide a throttle valve suitable for applications in which the communication, or source of high pressure working fluid, is controlled by a slidable gate-type valving disc having an opening moving into and out of alignment with a circular port in which the wire drawing effects of the action of the high pressure fluid are minimized by the valve design.